Nematic Fractional quantum Hall states at ν = 5/2 and 7/2 in ultraclean GaAs 2D hole systems

A hallmark of a high-quality, interacting 2D carrier system is the emergence of elusive even-denominator fractional quantum Hall states (FQHSs) whose quasiparticle excitations are expected to be non-Abelian anyons. These exotic states have potential applications in fault-tolerant topological quantum computing. One of the most prominent examples is the FQHS at the even-denominator filling factor ν = 5/2 observed in the excited (N = 1) Landau level of GaAs 2D electron systems. Recently, 2D hole systems in GaAs quantum wells have demonstrated significant potential for hosting a plethora of new even-denominator FQHSs [1], owing to unique characteristics and recent improvements in quality [2]. Here, we report the observation of FQHSs at ν = 5/2 and 7/2 in ultraclean GaAs 2D hole systems, evinced by deep minima in longitudinal resistances and developing Hall plateaus. Remarkably, the longitudinal resistances along [110] and [11-0] crystal directions exhibit significant anisotropy near and at v = 5/2 and 7/2 in the absence of any external, in-plane symmetry breaking magnetic field. Our observation signals the emergence of nematic FQHSs with spontaneously broken rotational symmetry. We surmise that mixing of heavy-hole and light-hole states, combining different orbital components in the wave function of one Landau level, may underlie these observations.

[1] C. Wang, A. Gupta, et al., Proc. Nat. Acad. Sci. USA 120, e2314212120 (2023)

[2] A. Gupta, C. Wang, et al.,Phys. Rev. Mater. 8, 014004 (2024)